(ORDO NEWS) — Scientists have traced the oldest wildfires ever discovered thanks to 430 million years of charcoal deposits from Wales and Poland. They give us valuable information about what life was like on Earth during the Silurian period.
In those days, the plant world was largely dependent on water for reproduction and probably did not appear in regions where part or all of the year was dry. The forest fires discussed in the study would burn very short vegetation, as well as rare knee- or waist-high plants.
The landscape would not be dominated by trees, but by the ancient fungus Prototaxites, the researchers say. Not much is known about this mushroom, but it is believed that it could grow up to nine meters (or almost 30 feet) in height.
“Now it seems that our evidence for the fire matches closely with our evidence for the earliest macrofossils of land plants,” says paleobotanist Ian Glasspool of Colby College in Maine.
“Once fuel is available, at least in the form of plant macrofossils, wildfires start almost instantly.”
Forest fires require fuel (plants), an ignition source (in this case, lightning strikes), and enough oxygen to burn.
The fact that the fires were able to spread and leave charcoal deposits suggests that the level of oxygen in the Earth’s atmosphere was at least 16 percent, the researchers said.
Today this level is 21 percent, but it has changed a lot during the history of the Earth. Based on the results of their analysis, the team believes that 430 million years ago, atmospheric oxygen levels could have been 21 percent or even higher.
This is very useful information for paleontologists. The thought is that plant growth and photosynthesis must have contributed more to the oxygen cycle around the time of these wildfires, and knowing the details of this oxygen cycle over time gives scientists a better idea of how life might have evolved.
“There must have been enough vegetation in the Silurian landscape for wildfires to spread and leave traces,” says paleontologist Robert Gastaldo, also of Colby College.
“At the time we are sampling, there was enough biomass around for us to have a forest fire record that we can identify and use to accurately determine the vegetation and process over time.”
The landscape of present-day Europe looked very different hundreds of millions of years ago, and the two sites that the researchers used for analysis must have been on the ancient continents of Avalonia and Baltica at the time these forest fires were raging.
Forest fires then, as now, contributed significantly to the carbon and phosphorus cycles, as well as to the movement of sedimentary rocks on the Earth’s surface. This is a complex combination of processes that requires a lot of unpacking.
The discovery certainly helps with this work – it beat the previous record for the oldest wildfire by 10 million years – and it also highlights the importance of wildfire research in mapping Earth’s history.
“Wildfires have long been an integral part of Earth system processes, and their role in these processes is almost certainly underestimated,” says Glasspool.
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